#18 - Concept Reference, Weaken

[Administrator]

Complete Question Explanation

The correct answer choice is (E).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D):

Answer choice (E): This is the correct answer choice.

This explanation is still in progress. Please post any questions below!

[tiffanystills]

Hi,

For this question I was in between answer choices C and E. I thought C weakened the stimulus because it somewhat described the species-energy hypothesis. C states there's a "higher energy influx, larger populations, and a lower probability of local extinction." I get how this would set the ground for the rate-of-speciation hypothesis by showing extinction doesn't become increasingly steep and there's larger populations, but the higher energy is what threw me off. I thought it could be an alternative cause (such as the species energy hypothesis).

E weakens the rate-of-speciation hypothesis by showing the extinction is rapid right? I thought just because it's rapid doesn't mean it negates speciation rates, which is what the theory says. I see how it can weaken but I'm just confused why C mentions energy. Thank you!

[Jeremy Press]

Hi Tiffany,

Answer choice C constitutes a slight "strengthener" for the species-energy hypothesis. It establishes a correlation between the elements mentioned in lines 25-27 of the passage ("greater energy influx leading to bigger populations, thereby lowering the probability of local extinction"). But it's just a correlation, so we don't know whether there's a causal link between those things, and that causal link ("energy influx leading to....thereby lowering") is what the passage says needs to be established. Answer choice C gets us only a very small part of the way toward establishing that causal linkage, so it can only very slightly strengthen the species-energy hypothesis.

Answer choice E is a better answer because it directly weakens the rate-of-speciation hypothesis as described in the last paragraph. Notice how it attacks the idea (in the last paragraph) that isolated groups in the tropics "are more likely to survive long enough to adapt to local conditions and ultimately become new species." Answer choice E shows that isolated groups are NOT more likely to survive (most suffer rapid extinction). A direct weakening of an essential element of a hypothesis constitutes a much stronger way to weaken that hypothesis than only slightly strengthening some alternative hypothesis.

I hope this helps!

Jeremy

[annabelle.swift]

Hi, I was between C and E.

For E: I ultimately eliminated this because I thought it only slightly weakened the rate-of-speciation hypothesis since it only discusses mammals. Can't the rate-of-speciation hypothesis still apply for reptiles or amphibians?

For C: I noted that this only talked about a correlation, but I thought that would be enough to strengthen the species-energy hypothesis because the passage admits that hypothesis is based on correlations anyway ("the species-energy hypothesis proposes the following positive correlations").

To me, both C and E slightly weakened the rate-of-speciation hypothesis. Can I have some advice on how to parse this question and others like it? Thank you!

[Robert Carroll]

annabelle.swift,

A Weaken answer doesn't have to say that all the facts are inconsistent with the position, just that enough are to cast doubt on the position to be weakened. Now, if the experience is mammals is exactly opposite what the rate-of-speciation hypothesis predicts, then this phenomenon is a counterexample to the hypothesis. It would be even better if ALL types of animals and even plants worked in a different way than the hypothesis predicts, but most mammals (themselves probably a large group) being different seems pretty bad for the argument.

All of the hypotheses are hypotheses about the causal mechanism underlying the difference in species numbers by latitude. Correlation can be evidence of causation ("correlation does not equal causation" is a common, and accurate, criticism of drawing too strong an inference from correlations, but it should not be taken to mean that correlation does not even provide any evidence of causation, which is definitely wrong). When the passage already brings up the correlation-related evidence, it's not trying to prove correlations, but use correlations to prove what the underlying causal connection is. So more evidence about correlation is not going to do anything - that's what the theories already had.

Robert Carroll